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T2FD antenna opinions solicited

I will hang T2FD in attic this weekend and have question about slope vs
bandwith. Well here is same post I just made to yahoo group. I have
some big dipoles for 75m and 160m, but I don't think they work so good
for SWL. I also have a very difficult time to climb up on roof
especially when cold. I'm a fraidy cat with heights( but no prob to
jump with a chute). This may be just an interm antenna till WX gets
better.

"Last time I was up in the attic about a year ago it looked like I
had about 12 foot of headroom. I was figuring I would put up a T2FD
about the full length 45 feet of attic and I could get a decent
slope. I was up there Saturday and now it looks like it's about 8
foot of headroom. I figure at the rate it's shrinking I better
hurry up and get the thing up while I can still stand up in the
attic.

So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

N9NEO wrote:
I will hang T2FD in attic this weekend and have question about slope vs
bandwith. Well here is same post I just made to yahoo group. I have
some big dipoles for 75m and 160m, but I don't think they work so good
for SWL. I also have a very difficult time to climb up on roof
especially when cold. I'm a fraidy cat with heights( but no prob to
jump with a chute). This may be just an interm antenna till WX gets
better.

"Last time I was up in the attic about a year ago it looked like I
had about 12 foot of headroom. I was figuring I would put up a T2FD
about the full length 45 feet of attic and I could get a decent
slope. I was up there Saturday and now it looks like it's about 8
foot of headroom. I figure at the rate it's shrinking I better
hurry up and get the thing up while I can still stand up in the
attic.

So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

I am looking for a comparison of the two potential installations.

Thanks & regards,
Bob
N9NEO

Is this a T2FD which you made (or are making) yourself, or is it from
RF Systems or B&W? I'm guessing home made since you talk about
changing the length.

I've used an RF Systems 45 foot T2FD at two different location with two
different angles because of the supports I had to work with, one maybe
20 degrees and the other at only 10 degrees!

Can't say that I noticed a difference. If anything, I'd say that I
pulled in more of the really low-power stations from Africa, South
America, Asia and the Pacific (omnidirectional) with it sloped at only
10 degrees all over the frequency range, from 60 meters to 19 meters
(never got anything that I'd consider low-power in the 16 meter band).
I did notice that I was able to DX in the 90 meter band only when the
angle was 20 degrees. Propogation always plays a huge part in whether
or not you receive a signal, but these results were pretty consistant.

I also believe that a big part in the exceptional signal-to-noise ratio
was the use of a Transi-Trap and a ground rod, even though the set-up
at 10 degrees had a pretty poor excuse for a rod (2 foot brass tube I
found at some hardware store, don't even know what it was supposed to
be used for).

I'd say use the full 45 feet with no slope.

BTW, where do you live? Its getting close to Spring everywhere here in
the States. Maybe six more weeks and you could set up your antenna
outside in relative warmth, if you're a Yankee like me :-)

So dilemma is length of antenna vs the slope. I can get a 20 degree
slope with a 23 foot antenna for about 14mc bottom end or a 30
degree slope with a 16 foot antenna for a 20mc bottom end. I am more
interested in SWL than ham bands. Antenna/attic is orientated along
a line parallel to 135/315 degrees."

I am looking for a comparison of the two potential installations.

Thanks & regards,
Bob
N9NEO

Since we're at the bottom of the sun spot cycle I'd guess an antenna
with a 14 mc bottom end would be better than 20 mc. If anything, I'd
extend it a bit to get it even lower, but you know what frequencies
you like listening to better than I do.

Actually Bob that is part of the problem. I am total newbie to SWL and
so I don't know which frequencies I would prefer the best. I'm usually
all over the place in any band I happen to find myself in. I seem to
have the most difficulty down in the shack with the higher
frequencies. Antenna situations for swl is not too good here. I have
160m inverted V, 75m dipole, and 5btv verticle. I'll stick the T2FD in
the attic for now and that should help near upper bands. Then I'll try
a long wire when WX gets better. Part of problem here I'm sure is bad
ground too, so lots of work needs to be done still.

First Build the Terminated Tilted Folded Dipole (T2FD)
as Big as you Can to get down to your "Lowest Desired
Operating Frequency" per the design Formulas.

Second the In-the-Attic T2FD is after all In-the-Attic and so . . .
It Ain't Gone-Ah-Be Tilted - It's Gone-Ah-Be FLAT [.]

QUESTION - What Did the Tilting Do For the T2FD ?
1 - Added to the Broadbanded Frequency Characteristics
of the T2FD Antenna.
2. Added to the Omni-Directional (All-Around 360 Degrees)
Characteristics of the T2FD Antenna.
Note - The TILT of the T2FD Antenna was usually about
30 Degrees and that would mean that the Height of the
Antenna "Vertical Dimension" was 50% of the Length of
the T2FD Antenna plus the Elevation at the Lower Base
(Bottom) Support.

Doing the Math - Your 45 Foot Long T2FD Antenna would
have to have a "Vertical Dimension" Drop of 22.5 Feet and
to keep the Wires overhead a minimum Lower Support
Height of 7.5 Feet for a Top Mounting Support Height of
at least 30 Feet. All sort of hard-to-do in most Attics.

* For example, an {T2FD} Antenna for the lower portion of
Shortwave (3 - 18 MHz) will be roughly 33m (110 feet) long,
with conductors spaced 1m (3.3 feet).
[With a Top End mounted about 60 Feet High at 30 Degrees.]

* In order to cover the higher portion of Shortwave (5 - 30 MHz),
this {T2FD} Antenna will be roughly 20m (66 feet) long,
with a spacing of 60 cm (24 inches).
[With a Top End mounted about 40 Feet High at 30 Degrees.]

If you explain the twist..... so I can understand. I don't think you
are telling me to just build a T2FD and make the feed point horizontal.
You are telling... Ok, I think I got it... So the loop will actually
go thru a 180 degree spin I think. is what you are telling me.

Yes, biggest problem was that roof wasn't high enough the last time I
was up there. I can stand up in it no prob and last weekend daughter's
BF and I laid a 24" wide path of plywood down the full 45 foot length.

Ok, I'll give this a try and see how it works out. I got some #43 ring
cores that I was going to build a 4:1 balun on. I may get bored one
day and fire up a transmitter into this setup, so I'll wind a few turns
on it so I don't smoke it.

If you explain the twist..... so I can understand. I don't think you
are telling me to just build a T2FD and make the feed point horizontal.
You are telling... Ok, I think I got it... So the loop will actually
go thru a 180 degree spin I think. is what you are telling me.

Yes, biggest problem was that roof wasn't high enough the last time I
was up there. I can stand up in it no prob and last weekend daughter's
BF and I laid a 24" wide path of plywood down the full 45 foot length.

Ok, I'll give this a try and see how it works out. I got some #43 ring
cores that I was going to build a 4:1 balun on. I may get bored one
day and fire up a transmitter into this setup, so I'll wind a few turns
on it so I don't smoke it.

thanks again
Bob

One other idea -- since your attic will have plenty of connection
points -- a fanned dipole; one for 12 meters, another for 17 meters;
feed both with one length of coax, no balun needed. And the two
dipoles should be within yelling distance of most of the upper
frequency swl listening bands, when you're not using the antenna for
ham things.

The T2FD style antennas are most popular for NVIS communication, where
the intent is to transmit and receive nearly straight up and back down
within a few hundred miles on freqs generally lower than 12MHz. The T2FD
does this best at lower elevations where itís less than .25 wavelength
above ground at highest operating frequency. Itís gained popularity with
military frequency hopping and ALE stations because of itís instant
broad band charm. With that said, one problem I see is placing the
antenna in the attic will put house wiring right underneath the antenna,
causing the pattern to point mostly up and not at a low angle to the
horizon where you want it for SWL DX (same for any horizontal ant in the
attic). It will also be more susceptible to RFI from stuff within the
house. The T2FD is generally a low noise antenna and it also requires
about a 16:1 balun, not a 4:1. You will seriously degrade the
performance if you try to feed it with anything less than the difficult
to obtain 16:1 flavor.
Bob

N9NEO wrote:
Ok, Thanks for the good links.

If you explain the twist..... so I can understand. I don't think you
are telling me to just build a T2FD and make the feed point horizontal.
You are telling... Ok, I think I got it... So the loop will actually
go thru a 180 degree spin I think. is what you are telling me.

Yes, biggest problem was that roof wasn't high enough the last time I
was up there. I can stand up in it no prob and last weekend daughter's
BF and I laid a 24" wide path of plywood down the full 45 foot length.

Ok, I'll give this a try and see how it works out. I got some #43 ring
cores that I was going to build a 4:1 balun on. I may get bored one
day and fire up a transmitter into this setup, so I'll wind a few turns
on it so I don't smoke it.